In a radio communication system, to enable a user equipment (UE, User Equipment) to measure downlink channel state information (CSI, Channel State Information), a base station needs to transmit a reference signal to the user equipment within its coverage area so that the user equipment measures a downlink channel.
For example, as specified in the long term evolution (LTE, Long Term Evolution) R10 protocol defined by the 3rd Generation Partnership Project (3GPP, the 3rd Generation Partnership Project), the base station needs to transmit a channel state information reference signal (CSI-RS, Channel State Information Reference signal) to the UE within its coverage area, so that the UE measures the downlink channel. In this case, the base station further needs to notify position information of the CSI-RS to the UE so that the UE can measure downlink channel state information according to the reference signal in the position.
To achieve a higher user throughput rate, a coordinated multiple point transmission and reception (CoMP, Coordinated Multiple Point transmission and reception) technology may be used in the radio communication system. The coordinated multiple point transmission and reception technology refers to that multiple nodes simultaneously provide data services for one or more users, where the nodes may be, for example, base stations, or remote radio heads (RRH, Remote Radio Head), or radio remote units (RRU, Radio Remote Unit) or antenna units (AU, Antenna Unit), or other types of cell serving nodes. With respect to the coordinated multiple point transmission and reception technology, the base station needs to use channel state information between a terminal and a candidate node and node set as an input or reference to complete processing such as resource allocation and data transmission. When the UE is served by different nodes or different node sets, the degree of interference received by the UE may vary, and the corresponding channel quality indicator (CQI, Channel Quality Indicator) may also vary. When interfering nodes use different transmission schemes (the transmission scheme of an interfering node may be muting, beamforming, transmit diversity, and so on), the degree of interference received by the UE may vary, and the corresponding CQI may also vary.
Referring to FIG. 1, FIG. 1 shows a conventional CoMP scenario, where nodes that may participate in coordinated data transmission are three conventional cells, a UE that accepts a CoMP service may be served by any one or more of the cells, and other cells are interfering cells. In the prior art, it is difficult for the UE to measure interference flexibly. For example, when the UE is served, if there is no downlink data transmission in an interfering cell, a physical downlink shared channel (PDSCH, Physical Downlink Shared Channel) of the interfering cell causes no interference to the UE, but a CRS of the interfering cell still causes interference to the UE. In this case, the UE is required to be capable of measuring interference in different scenarios accurately and flexibly, to obtain different CQIs in different scenarios. In the prior art, it is difficult for the UE to measure interference flexibly when the UE is served by any one or more cells.